1. Field of the Invention
This invention relates to a system capable of interchanging lenses of a camera, and more particularly to an electronic mount system performing data communication between a lens and the camera body.
2. Description of the Related Art
A camera system whose lens can be interchanged has been mainly employed in silver-halide single-lens reflex cameras. Since a variety of photographs that can exhibit the characteristics of each of the lenses can be taken it has been widely used.
Recently it is desired that the lens interchange system of the type described above be employed in a video camera for the purpose of taking novel animations.
However, when the lens interchange system is employed in the video camera, a problem arises in that the running of the tape with no picture taken occurs if the lens is not mounted on the camera body or the lens is not correctly mounted on the same. As a result, the tape needs to be rewound again to take a picture, so that the shutter chance is lost, or a problem arises in performing the concatenating recording, or a problem of excessive battery power consumption arises. In the case of a video camera in which an optical finder is employed, since a state of imaging cannot be checked, a problem arises in that un-focused images are unintentionally and continuously photographed.
The silver-halide single-lens reflex cameras take, in almost all cases, one second or less to complete the photographing Therefore, the separation of the lens during the photographing time due to some reason or the unintentional removal of the lens with the shutter thereof pressed cannot substantially occur.
On the other hand, since video cameras take a long time to photograph an image, the separation of the lens from the camera body is considerably probable.
Furthermore, when a recording trigger button is pressed once, the recording is continued if the button is not again pressed. For example, if the lens of the video camera is interchanged during a recording of an image with this video camera fixed by a tripod, unnecessary images during the lens interchanging work are recorded on the video tape. In order to overcome this problem, when the video tape is rewound and the recording is again started immediately before the interchange of the lens, the concatenating recording cannot be conducted satisfactorily.
Furthermore, if the power switch of the camera body is unintentionally switched on by the user or the like, power is consumed limitlessly while the camera is taking unnecessary images. In particular, in a case where the power source comprises a battery type source, the wasteful actuation of the camera body for a long time causes the battery to be excessively consumed. As a result, the battery is unintentionally exhausted when a necessary image is intended to be taken with this video camera.
In, the video camera system whose lens can be interchanged and of the type described above, various functions of the video camera (for example, white balance, shutter speed, AE (Automatic Exposure) and the like) need to be adjusted in accordance with the characteristics of the subject lens. In addition, the position of the lens interchanged and the diaphragm of the same needs to be initialized at a proper position so as to prevent malfunction of the control unit in the video camera.
However, the video camera system of the above-described conventional type encounters the following problems since the above-described various functions are not changed after the lens thereof has been changed:
(1) Since the various characteristics of the lens and the imaging conditions are usually varied after the lens has been interchanged, malfunctions can occur in the control system for the lens system in the camera body if the above-described functions which are arranged before the interchange of the lens are left intact.
(2) After the interchange of the lens, the user needs to again switch on the power for the purpose of resetting the functions, or a reset button or the like needs to be provided therein. Furthermore, a problem can occur in that a user forgets the setting of the functions.